Multistatic meteor radar observations to assess the spatial variability of mesospheric/lower thermospheric winds using a 3DVAR+div tomographic retrieval to measure spatially resolved 3D winds

<p>The middle atmospheric circulation is driven by atmospheric waves, which carry energy and momentum from their source to the area of their dissipation and thus providing an energetic coupling between different atmospheric layers. A comprehensive understanding of the wave-wave or wave-mean flow interactions often requires a spatial characterization of these waves. Multistatic meteor radar observations provide an opportunity to investigate the spatial and temporal variability of mesospheric/lower thermospheric winds on regional scales. We apply the 3DVAR+div retrievals to observations from the Nordic Meteor Radar Cluster and the Chilean Observation Network De Meteor Radars (CONDOR). Here we present preliminary results of a new 3DVAR+div retrieval to infer the vertical wind variability using spatially resolved observations. The new retrieval includes the continuity equation in the forward model to ensure physical consistency in the vertical winds. Our preliminary results indicate that the vertical wind variability is about +/-2m/s. The 3DVAR+div algorithm provides spatially resolved winds resolves body forces of breaking gravity waves, which are typically indicated by two counterrotating vortices. Furthermore, we infer horizontal wavelength spectra for all 3 wind components to obtain spectral slopes indicating a transition of the vertical to the divergent mode at scales of about 80-120 km at the mesosphere.</p>

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Measurements and Characterization of Turbulence in the Tip Region of an Axial Compressor Rotor

Journal of Turbomachinery ◽

10.1115/1.4037773 ◽

2017 ◽

Vol 139 (12) ◽

Cited By ~ 4

Author(s):

Yuanchao Li ◽

Huang Chen ◽

Joseph Katz

Keyword(s):

Strain Rate ◽

Shear Layer ◽

Turbulent Flows ◽

Reynolds Stress ◽

Suction Side ◽

Stress And Strain ◽

Spatial And Temporal Variability ◽

Mean Flow ◽

The Mean ◽

Stress And Strain Rate

Modeling of turbulent flows in axial turbomachines is challenging due to the high spatial and temporal variability in the distribution of the strain rate components, especially in the tip region of rotor blades. High-resolution stereo-particle image velocimetry (SPIV) measurements performed in a refractive index-matched facility in a series of closely spaced planes provide a comprehensive database for determining all the terms in the Reynolds stress and strain rate tensors. Results are also used for calculating the turbulent kinetic energy (TKE) production rate and transport terms by mean flow and turbulence. They elucidate some but not all of the observed phenomena, such as the high anisotropy, high turbulence levels in the vicinity of the tip leakage vortex (TLV) center, and in the shear layer connecting it to the blade suction side (SS) tip corner. The applicability of popular Reynolds stress models based on eddy viscosity is also evaluated by calculating it from the ratio between stress and strain rate components. Results vary substantially, depending on which components are involved, ranging from very large positive to negative values. In some areas, e.g., in the tip gap and around the TLV, the local stresses and strain rates do not appear to be correlated at all. In terms of effect on the mean flow, for most of the tip region, the mean advection terms are much higher than the Reynolds stress spatial gradients, i.e., the flow dynamics is dominated by pressure-driven transport. However, they are of similar magnitude in the shear layer, where modeling would be particularly challenging.

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Preliminary Results on Irradiance Measurements from Lyra and Swap

Advances in Astronomy ◽

10.1155/2012/623709 ◽

2012 ◽

Vol 2012 ◽

pp. 1-5 ◽

Cited By ~ 4

Author(s):

S. T. Kumara ◽

R. Kariyappa ◽

M. Dominique ◽

D. Berghmans ◽

L. Damé ◽

...

Keyword(s):

High Temporal Resolution ◽

Preliminary Results ◽

Spatially Resolved ◽

Large Yield ◽

Active Pixel ◽

Integrated Intensity ◽

Actual Contribution ◽

The Individual ◽

Aluminum Filter ◽

Full Disk

The first and preliminary results of the photometry of Large Yield Radiometer (LYRA) and Sun Watcher using Active Pixel system detector and Image Processing (SWAP) onboard PROBA2 are presented in this paper. To study the day-to-day variations of LYRA irradiance, we have compared the LYRA irradiance values (observed Sun as a star) measured in Aluminum filter channel (171 Å–500 Å) with spatially resolved full-disk integrated intensity values measured with SWAP (174 Å) and Ca II K 1 Å index values (ground-based observations from NSO/Sac Peak) for the period from 01 April 2010 to 15 Mar 2011. We found that there is a good correlation between these parameters. This indicates that the spatial resolution of SWAP complements the high temporal resolution of LYRA. Hence SWAP can be considered as an additional radiometric channel. Also the K emission index is the integrated intensity (or flux) over a 1 Å band centered on the K line and is proportional to the total emission from the chromosphere; this comparison clearly explains that the LYRA irradiance variations are due to the various magnetic features, which are contributing significantly. In addition to this we have made an attempt to segregate coronal features from full-disk SWAP images. This will help to understand and determine the actual contribution of the individual coronal feature to LYRA irradiance variations.

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Interhemispheric differences of mesosphere/lower thermosphere winds and tides investigated from three whole atmosphere models and meteor radar observations

10.5194/acp-2021-142 ◽

2021 ◽

Author(s):

Gunter Stober ◽

Ales Kuchar ◽

Dimitry Pokhotelov ◽

Huixin Liu ◽

Han-Li Liu ◽

...

Keyword(s):

General Circulation ◽

Climate Models ◽

Climate Model ◽

Lower Thermosphere ◽

Winter Season ◽

General Circulation Models ◽

Meteor Radar ◽

Radar Observations ◽

Seasonal Characteristics

Abstract. Long-term and continuous observations of mesospheric/lower thermospheric winds are rare, but they are important to investigate climatological changes at these altitudes on time scales of several years, covering a solar cycle and longer. Such long time series are a natural heritage of the mesosphere/lower thermosphere climate, and they are valuable to compare climate models or long term runs of general circulation models (GCMs). Here we present a climatological comparison of wind observations from six meteor radars at two conjugate latitudes to validate the corresponding mean winds and atmospheric diurnal and semidiurnal tides from three GCMs, namely Ground-to-Topside Model of Atmosphere and Ionosphere for Aeronomy (GAIA), Whole Atmosphere Community Climate Model Extension (Specified Dynamics) (WACCM-X(SD)) and Upper Atmosphere ICOsahedral Non-hydrostatic (UA-ICON) model. Our results indicate that there are interhemispheric differences in the seasonal characteristics of the diurnal and semidiurnal tide. There also are some differences in the mean wind climatologies of the models and the observations. Our results indicate that GAIA shows a reasonable agreement with the meteor radar observations during the winter season, whereas WACCM-X(SD) shows a better agreement with the radars for the hemispheric zonal summer wind reversal, which is more consistent with the meteor radar observations. The free running UA-ICON tends to show similar winds and tides compared to WACCM-X(SD).

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Doppler Radar Analysis of the Eyewall Replacement Cycle of Hurricane Matthew (2016) in Vertical Wind Shear

Monthly Weather Review ◽

10.1175/mwr-d-20-0289.1 ◽

2021 ◽

Author(s):

Ting-Yu Cha ◽

Michael M. Bell ◽

Alexander J. DesRosiers

Keyword(s):

Wind Shear ◽

Doppler Radar ◽

Vertical Wind Shear ◽

Radar Data ◽

Secondary Circulation ◽

Vertical Wind ◽

High Temporal Resolution ◽

Radar Observations ◽

Eyewall Replacement Cycle ◽

Replacement Cycle

AbstractHurricane Matthew (2016) was observed by ground-based polarimetric radars in Miami (KAMX), Melbourne (KMLB), and Jacksonville (KJAX) and a NOAA P3 airborne tail Doppler radar near the coast of the southeastern United States during an eyewall replacement cycle (ERC). The radar observations indicate that Matthew’s primary eyewall was replaced with a weaker outer eyewall, but unlike a classic ERC, Matthew did not reintensify after the inner eyewall disappeared. Triple Doppler analysis was calculated from the NOAA P3 airborne fore and aft radar scanning combined with the KAMX radar data during the period of secondary eyewall intensification and inner eyewall weakening from 19 UTC 6 October to 00 UTC 7 October. Four flight passes of the P3 aircraft show the evolution of the reflectivity, tangential winds, and secondary circulation as the outer eyewall became well-established. Further evolution of the ERC is analyzed from the ground-based single Doppler radar observations for 35 hours with high temporal resolution at a 5-minute interval from 19 UTC 6 October to 00 UTC 8 October using the Generalized Velocity Track Display (GVTD) technique. The single-Doppler analyses indicate that the inner eyewall decayed a few hours after the P3 flight, while the outer eyewall contracted but did not reintensify and the asymmetries increased episodically. The analysis suggests that the ERC process was influenced by a complex combination of environmental vertical wind shear, an evolving axisymmetric secondary circulation, and an asymmetric vortex Rossby wave damping mechanism that promoted vortex resiliency despite increasing shear.

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